An automatic faucet detects user's hands in a toilet or lavatory and a dish or a pan in a kitchen or the like to allow water to automatically run. Such an automatic faucet is widely used because of its convenience, cleanness, water-saving performance, and the like. As a sensor mounted to the automatic faucet to detect an object for which the water is allowed to run, an infrared sensor is used in almost all the cases.
Not only the automatic faucets but any faucet device is attached to a device for receiving running water and draining it, for example, to a washbowl or a washbasin in a toilet and to a sink in a kitchen.
FIG. 1 is a cross-sectional view showing a state where an automatic faucet according to a conventional example is attached to a washbasin. The reference numeral 10 denotes a washbasin. A faucet main body 11 of an automatic faucet is mounted to the washbasin 10. The faucet main body 11 has a sensor housing section 12 formed in its stem. In the sensor housing section 12, the above-described infrared sensor is housed. At a tip of the faucet main body 11, a spout 13 is provided.
It is preferred that a detecting direction of the sensor for emitting and receiving rays and a water running direction are parallel in view of convenience. As shown in FIG. 1, a ray emitting and receiving direction of the sensor is directed toward the washbasin 10. The sensor emits infrared rays. If an amount of reflected rays thereof exceeds a predetermined value, that is, if the amount of the reflected rays is large, it is generally determined that something is sensed. There is also a method of detecting not simply the amount of reflected rays but a change such as the movement of hands or the like (Unexamined Japanese Patent Publication No. Hei 7-233548). However, it is basically determined that something is sensed when the amount of reflected rays becomes large.
When the detection direction is viewed from the sensor, the surface of the washbasin 10 is present behind the hands corresponding to a target to be detected. However, since the distance from the sensor to the washbasin 10 is large compared with the distance to the hands, the amount of reflected rays of the infrared rays from the washbasin 10 is small. Therefore, normally, the sensor does not erroneously detect the washbasin 10. This is because material of a washbasin is generally a ceramic and infrared rays cause diffuse reflection on its surface as in the case of hands.
However, even if the washbasin is made of a ceramic, some kinds of ceramics are highly glossy. Furthermore, some washbasins are made of material other than ceramics, such as glass or stainless steel. Moreover, a kitchen sink is generally made of stainless steel. In such a case, even if the distance from the sensor to the washbasin or the sink is large, infrared rays emitted from the sensor cause specular reflection on their surfaces to generate reflected rays at an extremely high level. As a result, the sensor erroneously senses the washbasin, the sink or the like as an object such as a hand, and thus the automatic faucet erroneously allows water to run.
In order to avoid specular reflection, there is a method of orienting the sensor in another direction, for example, in a horizontal direction. However, the place where a user intends to wash their hands is in a washbasin because water splashes do not cause any trouble there. If the sensor is oriented in a direction other than the direction toward the washbasin, the action area of the user does not conform to the detection area of the sensor. Accordingly, it is extremely inconvenient to use.
In order to prevent an erroneous water flow, there are a sensor of which sensitivity can be adjusted at the place where the device is placed and a sensor in which signal processing has been modified as described in the above-mentioned Unexamined Japanese Patent Publication No. Hei 7-233548. However, they are effective only for small specular reflection. Thus, in practice, only the limited types of washbasin or sink can be used in combination with the automatic faucet. Moreover, the effects cannot be confirmed until the device is placed.
A method of selecting a sensor which does not use any ray reflection, such as an ultrasonic sensor, is also conceived. However, a sensor for the automatic faucet needs perfect waterproofing property, and the sensor is not allowed to have large size in view of design of the faucet. Accordingly, such a sensor is not preferred. Thus, in consideration of waterproofing property and the size, the infrared ray sensor is most suitable for the required specifications of the automatic faucet. Therefore, it has been an important issue to eliminate the effects of specular reflection.
The present invention was devised to solve the above problem and to provide an automatic faucet control device using a small infrared ray system sensor excellent in waterproofing property, which does not erroneously sense a washbasin or a sink of any materials as well as a control method thereof.